How To Build a Classroom Compost Bin

Composting is an eco-friendly way to reduce waste and create nutrient-rich garden soil. Building a compost bin is also a relatively simple do-it-yourself (DIY) project. In the video above, landscape contractor Jenn Nawada and carpenter Nathan Gilbert demonstrate how to build a large-scale compost bin for a school garden project, but you can use these basic steps to build the size you want.

Choosing the Right Location and Size

Before you start building your compost bin, figure out where you’re going to put it and how big it will be. 

Selecting the Ideal Spot

When choosing a location for your compost bin, consider the following factors:

• Accessibility: Place the bin in an easy-to-reach area to add materials and remove finished compost. This will encourage regular use.
• Drainage: Make sure the spot has good drainage to prevent waterlogging. Poor drainage can lead to soggy compost, which slows decomposition and causes unpleasant odors.
• Proximity: Choose a spot close to your kitchen or garden to make the process more convenient.
• Sun exposure: A partially shaded area is best, as it helps retain moisture without overheating the compost. Too much sun can dry out the compost, while too little can impede microbial activity.

Determining the Appropriate Size

Your compost bin’s size depends on how much organic waste you generate and your available yard space. For most home gardens, a 3-by-3-by-3-foot bin is enough. This size allows for good heat retention and airflow, which is vital to efficient composting. However, larger bins may be necessary for school or community gardens, where more substantial quantities of organic waste will accumulate.

If space is limited, consider building a vertical compost bin or using a compost tumbler that takes up less room. Make sure the bin is large enough to compost effectively, with at least 1 cubic yard of material to heat up and break down properly.

Materials and Tools Needed for a Compost Bin

The right materials and tools are important for building a sturdy and long-lasting compost bin. Here’s what you’ll need:

Materials

• Cedar lumber (2x6s, 4x4s, and 1x6s)
• Exterior-grade brad nails
• Exterior-grade plywood
• Nailing cleat
• Piano hinge
• Stainless steel screws

Tools

• Finish nailer
• Impact driver
• Miter saw
• Sander
• Screwgun
• Table or circular saw
• Tape measure

Using high-quality materials will help your compost bin withstand the elements and frequent use. Cedar lumber, for instance, is naturally rot- and pest-resistant, making it great for outdoor projects.

Building the Compost Bin Frame

Creating a strong frame is the foundation of a well-constructed compost bin. Follow these steps to build the frame:

1. Cut the 2×6 cedar boards to the desired length for the bin’s back and sides. Accurate cuts guarantee all parts fit together correctly.
2. Assemble the frame by attaching the side boards to the backboards using screws. This forms the basic bin structure.
3. Install 4×4 posts in the back corners for added stability. These posts provide support and help the bin withstand the compost materials’ weight.
4. Continue adding boards to the sides and back, using spacers between each board for consistent spacing and airflow. This promotes proper aeration, which is key for composting.

Pro tip: Pre-drill the screw holes to prevent the wood from splitting, creating a more durable structure.

Creating the Front Panels

The front panels of your compost bin should be removable for easy access to the compost. Here’s how to create them:

1. Cut two pieces of 2×6 cedar to the overall bin height for each front corner. This will create snug-fitting panels.
2. Rip one of the 2x6s to 2 1/2 inches wide, leaving the other cut-off side at 3 inches wide. This will create effective channels.
3. Fasten the 2 1/2-inch piece in the center of the full-width 2×6, aligning the 3-inch-wide piece so there’s a 1/2-inch that overhangs the 2 1/2-inch piece’s edge. This design forms channels for the front panels to slide into.
4. Repeat this process for the other corner and create a third channel post for the middle, sandwiching a 2 1/2-inch board between two full-width 2x6s to create dual channels.
5. Cut the front panels to fit between the channels, sanding the edges lightly to help them slide easily. Removable panels simplify the process of turning and harvesting compost.

Adding the Top and Finishing Touches

A well-designed top maintains correct moisture levels and temperature in your compost bin. Here’s how to create and install the top:

1. Cut a piece of exterior-grade plywood to cover the entire compost bin. This protects the compost from excessive rain and sun.
2. Divide the plywood sheet in half and attach a piano hinge to both sides, allowing users to flip open one side at a time for easy filling. This design means you can add materials without fully opening the bin.
3. Sand any rough edges to prevent splinters and boost the bin’s appearance.

Proper Composting Techniques

Building the bin is just the first step. Here are some tips for using your bin to compost.

Balancing Green and Brown Materials

For successful composting, keep a proper balance of green and brown materials:

• Green materials: Grass clippings, fresh leaves, and kitchen scraps (excluding meat, dairy, and oils). These are rich in nitrogen and help activate the composting process.
• Brown materials: Dry leaves, twigs, and paper products. These provide carbon, which is essential for feeding the microbes that decompose the organic matter.

The ideal ratio is 3 parts brown to 1 part green materials. Achieving this balance encourages effective decomposition and minimizes odors.

Maintaining Your Compost Pile

To make sure your compost breaks down efficiently, follow these best practices:

• Turn the pile regularly to aerate it and distribute moisture evenly. This introduces oxygen, a critical element in composting.
• Monitor moisture levels, keeping the pile as damp as a wrung-out sponge. Ideal moisture levels foster microbial activity and prevent the compost from becoming too dry or too soggy.
• Add water if the pile becomes too dry or more brown materials if it becomes too wet. This helps maintain the balance necessary for efficient composting.

Additionally, chopping larger materials before adding them to the bin can speed up the decomposition process. Smaller pieces have a larger surface area for microbes to work on, leading to faster breakdown.

Benefits of Composting

Composting has many advantages for both your garden and the environment, supporting both sustainability and soil health. Here are some notable benefits:

• Reduces waste sent to landfills: Composting converts organic waste into valuable soil, reducing landfill waste.
• Creates nutrient-rich soil for plants: Compost adds essential nutrients to the soil, promoting healthier plant growth.
• Improves soil structure and water retention: Compost increases the soil’s ability to retain water, reducing watering frequency.
• Promotes beneficial microorganisms in the soil: These microorganisms aid in breaking down organic material and improving soil health.
• Reduces the need for chemical fertilizers: By enriching the soil naturally, compost reduces the reliance on synthetic fertilizers and keeps your garden more organic.

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